U.S. patent application number 11/725748 was filed with the patent office on 2007-09-27 for two-way valved catheter.
This patent application is currently assigned to Cook Vascular Incorporated. Invention is credited to Chun Kee Lui.
Application Number | 20070225678 11/725748 |
Document ID | / |
Family ID | 38445796 |
Filed Date | 2007-09-27 |
United States Patent
Application |
20070225678 |
Kind Code |
A1 |
Lui; Chun Kee |
September 27, 2007 |
Two-way valved catheter
Abstract
A catheter and method for transporting a fluid between a body
vessel of a patient and a site external of the patient. The
catheter comprises a catheter body sized to at least partially
extend between the body vessel and the external site. The catheter
body has a proximal portion extending toward the external site and
a distal portion extending to the body vessel. An inwardly
contoured segment is formed in the catheter body at the distal
portion, and a valve is formed at the inwardly contoured segment.
The valve is operable to open in a first direction when subjected
to a first pressure from a side of the valve to permit fluid flow
therethrough in the first direction, and in a second direction
opposite the first direction when subjected to a second pressure
from another side of the valve to permit fluid flow therethrough in
the second direction.
Inventors: |
Lui; Chun Kee; (Monroeville,
PA) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE/INDY/COOK
ONE INDIANA SQUARE, SUITE 1600
INDIANAPOLIS
IN
46204-2033
US
|
Assignee: |
Cook Vascular Incorporated
Leechburg
PA
|
Family ID: |
38445796 |
Appl. No.: |
11/725748 |
Filed: |
March 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60785196 |
Mar 23, 2006 |
|
|
|
Current U.S.
Class: |
604/523 ;
604/537 |
Current CPC
Class: |
A61M 25/0075 20130101;
A61M 25/0021 20130101; A61M 2025/0034 20130101; A61M 25/0032
20130101; A61M 25/0023 20130101; A61M 25/003 20130101; A61M 25/0054
20130101 |
Class at
Publication: |
604/523 ;
604/537 |
International
Class: |
A61M 25/00 20060101
A61M025/00; A61M 25/16 20060101 A61M025/16; A61M 25/18 20060101
A61M025/18 |
Claims
1. A catheter for use in fluid transport between a body vessel of a
patient and a site external of the patient, comprising: a catheter
body sized to at least partially extend between said body vessel
and said external site, said catheter body having a proximal
portion extending toward said external site and a distal portion
extending to said body vessel, said catheter body comprising an
inwardly contoured segment at said distal portion; and a valve
formed at said inwardly contoured segment, said valve operable to
open in a first direction when subjected to a first pressure from a
side of the valve to permit fluid flow therethrough in said first
direction, said valve operable to open in a second direction,
opposite to said first direction, when subjected to a second
pressure from another side of the valve to permit fluid flow
therethrough in said second direction, said valve structured to
remain substantially closed in the absence of said first and second
pressures.
2. The catheter of claim 1, wherein said valve comprises a
longitudinal slit formed at said contour.
3. The catheter of claim 1, wherein said catheter is formed of a
performance material.
4. The catheter of claim 1, wherein said catheter is formed of a
thermoplastic polymer.
5. The catheter of claim 3, wherein said catheter is formed of
polycarbonate urethane.
6. The catheter of claim 2, wherein a longitudinal portion of said
catheter axially adjacent to said inwardly contoured segment is
buttressed.
7. The catheter of claim 2, wherein a longitudinal portion of said
catheter beyond each axial end of said inwardly contoured segment
is buttressed.
8. The catheter of claim 2, wherein said catheter comprises a
co-extrusion, said co-extrusion comprising a relatively stiff outer
catheter portion, and comprising a relatively soft inwardly
contoured segment.
9. The catheter of claim 2, wherein said catheter comprises two
lumens, and wherein said valve provides communication between a
first one of said lumens and a space exterior of said catheter,
further comprising a second valve for providing communication
between a second one of said lumens and a space exterior of said
catheter.
10. The catheter of claim 9, wherein said second valve comprises a
one-way valve.
11. A method of forming a two-way valved catheter suitable for use
in transporting a fluid between a body vessel of a patient and a
site external of the patient, comprising: providing a tubular
catheter body, said catheter body sized such that a proximal
portion extends substantially to said external site and a distal
portion extends to said body vessel; forming an inwardly contoured
segment at said distal portion of said tubular catheter body; and
forming a valve at said inwardly contoured segment, said valve
comprising a longitudinal slit formed in said segment, said valve
being sized and dimensioned such that upon exposure to a first
predetermined pressure from a first side thereof, said valve opens
in a first direction to permit fluid flow therethrough in said
first direction, and upon exposure to a second predetermined
pressure from a second side thereof, said valve opens in a second
direction, opposite to said first direction, to permit fluid flow
therethrough in said second direction, said valve structured to
remain closed in the absence of said predetermined first and second
pressures.
12. The method of claim 11, wherein said valve is formed by:
positioning a distal portion of said catheter in a mold; molding
said distal portion to form said inwardly contoured segment; and
cutting said slit in said inwardly contoured segment.
13. The method of claim 12, wherein said molding step comprises:
positioning a mandril in an interior space of said distal portion,
said mandril sized and shaped for forming said inwardly contoured
segment; and molding said segment with said mandril positioned
therein.
14. The method of claim 11, wherein said tubular catheter body is
formed by extrusion.
15. The method of claim 14, wherein the extruded tubular catheter
body is partially cured, and said inwardly contoured segment is
formed in said partially cured catheter body, and wherein said
catheter body having said inwardly contoured segment formed therein
is substantially fully cured.
16. The method of claim 11, wherein said catheter body is formed
from a performance material.
17. The method of claim 11, wherein said catheter body is formed
from a polycarbonate urethane.
18. The method of claim 11, wherein said tubular catheter body
comprises a co-extrusion, and wherein said inwardly contoured
segment is relatively soft, and a non-contoured outer portion is
relatively stiff.
19. The method of claim 11, wherein said tubular catheter body
comprises two lumens, and wherein said valve provides communication
between one of said lumens and a space exterior of said catheter,
and wherein a second valve is formed in said catheter body for
providing communication between the other lumen and a space
exterior of said catheter.
20. The method of claim 19, wherein said second valve comprises a
one-way valve.
Description
RELATED APPLICATION
[0001] The present patent document claims the benefit of the filing
date under 35 U.S.C. .sctn. 119(e) of Provisional U.S. Patent
Application Ser. No. 60/785,196, filed Mar. 23, 2006, which is
hereby incorporated by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] This invention relates generally to a catheter having a
valve for controlling the flow of a fluid therethrough, and more
particularly, to a catheter fabricated from a performance material
having a two-way valve formed therein.
[0004] 2. Background Information
[0005] Valved catheters are well known in the medical arts.
Typically, a valve is positioned in a lumen of a catheter to
selectively control, or prevent, the unidirectional flow of fluid
through the lumen. Some catheters are provided with two-way valves.
Two-way valves are structured to permit fluid to flow therethrough
in either direction upon occurrence of a designated condition,
typically upon the occurrence of a predetermined pressure
differential between the respective sides of the valve.
[0006] One such two-way valve is described in U.S. Pat. No.
4,549,879 to Groshong. The catheter in the '879 patent is formed of
a soft, flexible material (silicone rubber), and has a slit valve
formed in a catheter wall. The slit valve is closed under normal
physiologic pressures. In this event, the catheter walls on either
side of the slit are in registry with each other, and fluid cannot
pass through the valve. When sufficient pressure gradients are
applied across the slit valve, the catheter walls deform such that
the slit valve surfaces are no longer in registry, and an orifice
is formed through which fluid may flow into, or out of, the
catheter. As shown in FIG. 4b of the '879 patent, the valve opens
outwardly when the fluid pressure inside the catheter exceeds the
fluid pressure outside the catheter by a predetermined amount. As a
result, a pressurized fluid within the catheter infuses through the
valve to the region exterior of the catheter. Similarly, as shown
in FIG. 4c, when the pressure differential outside the catheter
exceeds that interiorly of the catheter by a predetermined amount,
the valve opens inwardly to permit aspiration of a fluid, such as
blood, into the interior of the catheter.
[0007] There are some disadvantages associated with the use of
two-way valves in soft, flexible catheters. For example, since the
catheter of the '879 patent is formed of a soft material, the
catheter cannot be easily navigated through the vasculature. In
order to generate sufficient force to push the catheter through a
vessel, a stiffening wire must be inserted into the lumen of the
catheter in a manner such that it abuts the closed end of the
catheter. A force is exerted against the wire, and thus against the
closed catheter end, to direct the catheter along the desired
pathway. Another disadvantage associated with the use of valves
formed from such soft materials, is that such valves are subject to
unintended opening generated by unexpected and/or involuntary
physical phenomena, such as coughing, on the part of the
patient.
[0008] Higher performance catheter materials have sufficient
strength to overcome these disadvantages; however such performance
materials are often too stiff to allow reliable operation of a
two-way valve. For example, the pressure differentials required to
open such valves may be undesirably high. In addition, the valves
may lack the flexibility to reliably return to their original
sealed condition following cessation of the pressure. Still
further, the lack of flexibility of such valves renders them
subject to leakage. Even if such catheters can be structured to
operate as a valve, such valves may only be reliable for re-sealing
after fluid flow in a first direction, and are not operable as
two-way valves.
[0009] Long-term implantable catheters have traditionally been
fabricated from silicone (a thermoset material), or thermoplastic
polyether-based polyurethane. The Groshong catheter described above
is an example of a catheter formed from silicone. The Groshong
catheter was fabricated from a soft silicone because that
composition was necessary for that valve to work, i.e., the
catheter was designed for the valve. Polyether-based polyurethane
catheters typically exhibit some properties superior to those of
silicone, e.g., higher tensile strength and fatigue resistance.
However, polyether-based polyurethane is subject to stress cracking
when used in long-term implants in the human body.
[0010] It is desired to provide a catheter having a two-way valve
formed therein, in which the catheter is formed of a material
having a high degree of strength and pushability, and does not
exhibit appreciable stress-cracking upon long-term implantation. It
is further desired to provide a catheter formed from a material
wherein the two-way valve is structured such that it opens upon
exposure to a desired pressure differential that may be generated
from either side of the valve, and reliably re-seals upon release
or diminution of the pressure.
SUMMARY
[0011] The present invention addresses the problems existing in the
art. In one form thereof, the invention comprises a catheter for
use in transporting a fluid between a body vessel of a patient and
a site external of the patient. The catheter comprises a catheter
body sized to at least partially extend between the body vessel and
the external site. The catheter body has a proximal portion
extending toward the external site and a distal portion extending
to the body vessel. An inwardly contoured segment is formed in the
catheter body at the distal portion, and a valve is formed at the
inwardly contoured segment. The valve is operable to open in a
first direction when subjected to a first pressure from a side of
the valve to permit fluid flow therethrough in the first direction,
and in a second direction opposite the first direction when
subjected to a second pressure from another side of the valve to
permit fluid flow therethrough in the second direction.
[0012] In another form thereof, the invention comprises a method of
forming a two-way valved catheter for transporting a fluid between
a body vessel of a patient and a site external of the patient. A
tubular catheter body sized such that a proximal portion extends
substantially to the external site and a distal portion extends to
the body vessel is provided, and an inwardly contoured segment is
formed at the distal portion of the tubular catheter body. A valve
is formed at the inwardly contoured segment, which valve comprises
a longitudinal slit formed in the contoured segment. The valve is
sized and dimensioned such that upon exposure to a first
predetermined pressure from a first side thereof, the valve opens
in a first direction to permit fluid flow therethrough in the first
direction, and upon exposure to a second predetermined pressure
from a second side thereof, the valve opens in a second direction,
opposite to the first direction, to permit fluid flow therethrough
in the second direction. The valve is structured to remain closed
in the absence of the predetermined first and second pressures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a side elevational view of the distal end of a
catheter according to an embodiment of the present invention,
showing the two-way valve in the closed position;
[0014] FIG. 2 is a sectional view taken along line 2-2 of FIG.
1;
[0015] FIG. 3 is a sectional view taken along line 3-3 of FIG.
1;
[0016] FIG. 4 is a sectional view of a mold and mandril for forming
the two-way valve in the catheter, showing the catheter positioned
between upper and lower mold portions;
[0017] FIG. 5 is an enlarged view of mandril 20;
[0018] FIG. 6 is an enlarged cross-sectional view of the contoured
portion of the catheter body following removal from the mold;
[0019] FIG. 7 is a side elevational view of the distal end of
another embodiment of a valved catheter according to an embodiment
of the present invention;
[0020] FIG. 8 is a sectional view taken along line 8-8 of FIG.
7;
[0021] FIG. 9 is a sectional view of another embodiment of a valved
catheter, wherein the catheter is co-extruded from a stiff and a
soft material;
[0022] FIG. 10 is a side elevational view of the distal end of
another embodiment of a valved catheter according to an embodiment
of the present invention, wherein the catheter includes a one-way
valve and a two-way valve;
[0023] FIG. 11 is a top view of the catheter of FIG. 10; and
[0024] FIG. 12 is a sectional view taken along line 12-12 of FIG.
10.
DETAILED DESCRIPTION OF THE DRAWINGS AND THE PRESENTLY PREFERRED
EMBODIMENTS
[0025] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings, and specific language will
be used to describe the same. It should nevertheless be understood
that no limitation of the scope of the invention is thereby
intended, such alterations and further modifications in the
illustrated device, and such further applications of the principles
of the invention as illustrated therein being contemplated as would
normally occur to one skilled in the art to which the invention
relates.
[0026] In the following discussion, the terms "proximal" and
"distal" will be used to describe the opposing axial ends of the
catheter, as well as the opposing axial ends of various component
features. The term "proximal" is used in its conventional sense to
refer to the end of the catheter (or component thereof) that is
closest to the operator during use of the device. The term "distal"
is used in its conventional sense to refer to the end of the
catheter (or component thereof) that is initially inserted into the
patient, or that is closest to the patient.
[0027] FIG. 1 is a side elevational view of the distal end portion
of a catheter 10, according to an embodiment of the present
invention. Catheter 10 includes a tubular catheter body 11 having a
lumen 16 formed therein, and a distal tip 14 welded or otherwise
securely engaged at the distal end of tubular catheter body 11.
Preferably, distal tip 14 is formed from the same or a similar
composition used to form catheter body 11.
[0028] Catheter body 11 includes a valve slit 12 disposed
proximally of distal tip 14. Valve slit 12 is provided in an
inwardly contoured segment 13 of the distal end portion of catheter
body 11. As used herein, an "inwardly contoured" segment refers to
a segment of the catheter body that is inverted, depressed or
otherwise sunken with respect to the remainder of the catheter
body. The inwardly contoured segment is best shown in FIG. 2, taken
along line 2-2 of FIG. 1. For comparison, FIG. 3, taken along line
3-3 of FIG. 1, illustrates the remainder of (non-contoured)
catheter body 11 proximal of contoured segment 13 in cross section.
The inwardly contoured segment extends in the proximal direction a
selected distance from distal tip 14 of catheter 10, such as about
one-half inch (1.3 cm). In FIGS. 1 and 2, valve slit 12 is shown in
its closed position. If desired, the inwardly contoured portion may
extend all the way to the distal end of catheter 10.
[0029] Unlike thermoset silicone elastomers that have been
conventionally utilized to form catheters having two-way valves,
the present invention preferably utilizes a thermoplastic material
that is capable of exhibiting superior mechanical properties when
compared to the prior materials. Thermoplastic and thermoset
materials are processed quite differently. In a preferred
embodiment, the material used to form the inventive catheter
comprises a performance material capable of functioning in reliable
fashion as a two-way valve, and that is also suitable for long-term
implantation without appreciable stress-cracking. As the term is
used herein, a "performance material" is a material having
sufficient pushability to enable the catheter to be directed
through a vessel, sufficient tensile strength to resist compressive
forces typically encountered upon passage through the vessel,
sufficient freedom from stress-cracking under normal conditions
encountered within a vessel to enable long-term (e.g., at least 30
days or more) implantation of the catheter, and which is capable of
having a two-way valve formed therein, which valve is capable of
opening in a first direction in response to a desired pressure
differential across the valve originating from one side of the
valve, and opening in a second direction in response to a desired
pressure differential across the valve originating from an opposite
side of the valve, and reseals when the pressure differential is
not present.
[0030] Particularly preferred performance materials comprise a
class of materials known as polycarbonate urethanes. Polycarbonate
urethanes are thermoplastic elastomers formed as the reaction
product of a hydroxyl terminated polycarbonate, an aromatic
diisocyanate, and a low molecular weight glycol used as a chain
extender. The carbonate linkages adjacent to the hydrocarbon groups
give this class of materials high oxidative stability, rendering
them particularly beneficial in applications such as long-term
implantation, wherein oxidation may otherwise lead to premature
degradation. The materials also have high biocompatibility,
pushability and mechanical strength. Further discussion of
polycarbonate urethanes, and their preparation, is provided in,
e.g., U.S. Pat. Nos. 5,133,742 and 4,810,749, incorporated by
reference herein. Polycarbonate urethanes suitable for use herein
are available commercially from, e.g., The Polymer Technology
Group, of Berkeley, CA, under the trademark BIONATE.RTM., and from
the CT Materials division of Cardiotech International Inc., under
the trademark CHRONOFLEX.RTM.. CHRONOFLEX.RTM. polycarbonate
urethanes are available as an aliphatic thermoplastic polymer
(CHRONOFLEX.RTM. AL), and as an aromatic thermoplastic polymer
(CHRONOFLEX.RTM. AR).
[0031] In addition to the commercial products listed above,
suitable polycarbonate urethanes can be custom synthesized in known
manner to optimize the specific properties desired for a particular
application. Although polycarbonate urethanes comprise the
preferred materials for use herein, other performance materials
capable of exhibiting the properties described herein may be
substituted.
[0032] When an inwardly contoured catheter is formed as described
hereinafter, the catheter comprises a reliably-functional two-way
valve that is built into the wall of the catheter. The valved
catheter has the strength, durability and freedom from
stress-cracking not shown in prior art valved catheters, such as
silicone valved catheters and catheters formed from other
conventional non-performance materials.
[0033] As stated, the two-way valve comprises a longitudinal slit
in an inwardly contoured segment of the catheter body. The slit is
structured such that the valve opens when subjected to a
predetermined positive or negative pressure, and remains closed
when there is no pressure differential across the valve, or where a
pressure differential exists, but the differential is less than a
predetermined level required for opening the valve in the desired
direction. The formation of one-way valves in performance catheters
is relatively straightforward, and generally does not give rise to
troublesome structural issues. However, providing a two-way valve
in such catheters to permit fluid to flow in both directions, and
to effectively re-seal following such flow, has been problematic.
The present performance catheter is structured in a manner to
overcome such problems by permitting such two-way flow, and
effectively re-sealing following the flow. By providing the slit in
an inwardly contoured segment of the catheter as described, and by
structuring the walls of the catheter in a manner such that the
slit is disposed at particular geometries relative to the wall, a
very reliable and efficient two-way valve is formed.
[0034] In a preferred embodiment, the two-way valve may be formed
in the following manner. The inwardly contoured segment of the
catheter body is initially formed into a desired shape. One
preferred manner in which this portion may be shaped is by the
application of heat and pressure in a mold. One arrangement for
accomplishing this is illustrated in FIG. 4. A suitably sized and
shaped mandril 20 is inserted inside the portion 13 of catheter
body 111 to be contoured, and the catheter portion is positioned in
a suitably sized and shaped mold 24. Mold 24 has an upper mold
portion 26 and a lower mold portion 28. As illustrated, catheter
portion 13 is positioned in a suitably-shaped cradle 29 formed in
lower mold portion 28. Upper mold portion 26 is shaped to include
voids 25, and a projecting portion 27. When the mold is closed as
illustrated in the figure, heat and pressure are applied in
conventional fashion to mold inwardly contoured segment 13 from the
tubular catheter body 11. Following cessation of the heat and
pressure, the mold and the catheter are cooled, and the upper mold
portion is removed. Prior to removing the mandril from the
catheter, the valve slit may then be cut through the catheter wall
of the contoured portion using a knife or other straight-edge
device. Those skilled in the art can readily arrive at appropriate
molding conditions for a particular catheter, such as the molding
time and temperature, without undue experimentation, taking into
account relevant factors such as the type and composition of
catheter, and the specific shape intended to result therefrom.
[0035] The formation of an effective two-way valve can be
problematic. It is, or course, important that the valve be capable
of opening sufficiently to enable flow of fluid in each direction
through the valve, and properly re-sealing following fluid flow.
The valve of the present invention is formed in the catheter in a
manner that provides a very specific contour. This contour enables
the valve to function effectively in both directions. For best
results, the cross-sectional dimensions of the valved catheter may
be optimized for the particular material from which the catheter is
formed. In other words, the specific dimensions, shape, etc., of
the inwardly-contoured segment that are required to form an
effective two-way seal may vary from material to material. When the
teachings of the present invention are utilized, no more than
routine experimentation with a particular composition will be
required to determine optimal parameters for that composition.
[0036] FIG. 6 illustrates an enlarged cross-sectional view of the
inwardly contoured segment 13 of a polycarbonate urethane catheter
body 11 following molding. FIG. 5 is an enlarged view of mandril 20
which has been removed from inwardly contoured segment 13 to arrive
at the view of FIG. 6. In this embodiment, mandril 20 is fabricated
from 0.062 inch (1.6 mm) outer diameter ("OD").times.0.042 inch
(1.1 mm) inner diameter ("ID") stainless steel tube. Preferably,
mandril 20 has a length that exceeds the length of inwardly
contoured segment 13. This additional length provides stability to
the catheter adjacent to the contoured portion. In the embodiment
shown, dimension "A" of mandril 20 in FIG. 5 is 0.040 inch (1
mm).
[0037] In a preferred embodiment, the catheter body 11 from which
inwardly contoured segment 13 is formed has an OD of 0.100 inch
(2.5 mm) and an ID of 0.062 inch (1.6 mm). As further illustrated
in FIG. 6, following molding of the contoured portion, catheter
body 11 has dimension "B" of 0.078 inch (2 mm), dimension "C" of
0.1 16 inch (2.9 mm), and dimension "D" of 0.052 inch (1.3 mm).
Mold 24, and more particularly, mold projecting portion 27 (FIG.
4), are sized and dimensioned such that the radius "R" of contoured
portion 13 in the embodiment shown is 0.031 inch (0.8 mm). By
providing dimensions as described herein, the two-way valve
functions very favorably in both directions when the performance
material comprises a polycarbonate urethane. Thus, valve slit 12
will open when subjected to a predetermined positive or negative
pressure, but will remain closed when the pressure differential
across the valve is below the predetermined level. Those skilled in
the art will appreciate that the dimensions provided herein are
exemplary only, and that other dimensions may be appropriate for a
particular performance material.
[0038] It is known in the art to form a valve by cutting a
longitudinal slit through a tubular wall of a catheter. Typically,
however, such valves only operate efficiently to control fluid flow
in a single direction. Thus, for example, when a fluid is to be
injected from a catheter into a vessel, the valve opens outwardly
to permit such fluid flow when the pressure of the fluid inside the
catheter exceeds the pressure on the outside of the catheter. When
the fluid flows through the valve in this direction, the valve
normally operates in a very efficient manner to permit the
requisite fluid flow, and to re-seal once the pressure has been
relieved. On the other hand, when fluid is to be aspirated from the
vessel into the catheter, the higher exterior pressure tends to
hold the slit closed, and the walls which configure the slit
essentially form an arch. In this event, the valve may not permit
efficient aspiration of the fluid, and even if so, may not re-seal
properly following flow of the fluid through the valve. However, by
locally reshaping the wall of the catheter to form an inwardly
contoured shape as described herein, the arch effect can be
overcome such that the walls which configure the valve are
deflectable in an inward direction. The (un-contoured) catheter
wall longitudinally adjacent to the contoured portion provides
sufficient structure to minimize inward deflections of the
supporting catheter wall, thereby preventing the valve from
pinching tighter than desired and failing to open. The valve
opening pressures are a function of the dimensions and geometry of
the valve, as well as the modulus (stiffness) of the material from
which the catheter is formed. In practice, the valve walls should
have reasonable thickness so that even if the two sides of the slit
are slightly mismatched, the slit will not leak. Those skilled in
the art can readily determine an appropriate thickness without
undue experimentation when following the teachings of this
invention.
[0039] While a catheter material having various combinations of
dimensions can provide the requisite performance characteristics,
the optimal conditions for a particular catheter may be influenced
by the material from which the catheter is formed. Preferably, the
catheter is formed from a material that is shapeable to form an
inwardly contoured segment as described. The particular material
that may be utilized in a catheter may be determined utilizing no
more than routine experimentation when the teachings of the present
invention are followed. Thus, variables such as the modulus of the
catheter material, shape and radius of the contour, thickness of
the walls, etc., may be varied as desired to provide an optimal
catheter and two-way valve for a particular material.
[0040] As stated above, it is preferred to form the catheter from a
performance material, such as polycarbonate urethane. However, the
catheter need not necessarily be formed from a performance
material, as long as the material utilized is capable of forming an
effective two-way valve when contoured as described herein. One
example of a suitable non-performance material is silicone, a
thermoset material. When a silicone catheter is utilized, the
catheter is preferably formed by extrusion. However, in this case
the extruded catheter will only be partially cured. This is
accomplished by monitoring the time and temperature of the curing
operation, and then removing the catheter before full curing has
taken place. One end of the partially-cured catheter may then be
re-shaped in a mold to form the inward contour as described, and
the entire catheter may then be heated to arrive at the final
curing.
[0041] According to the preferred embodiment described above, the
inwardly contoured segment may be formed by molding a generally
cylindrical tube/catheter. However, there are numerous other ways
in which a catheter may be provided with an inwardly contoured
segment, any such methods being within the scope of the invention.
For example, a length of catheter tubing can be extruded to have
one or more inwardly contoured segments, or depressions, disposed
intermittently along the length of the tubing. This tubing can then
be cut into individual catheters, each one of which includes an
inwardly contoured segment as described. Those skilled in the art
are readily able to arrive at other such methods utilizing no more
than routine experimentation.
[0042] In an alternative embodiment of the present invention, a
catheter 40 may be provided in which the entire length of the
catheter is extruded or otherwise formed to include the
cross-sectional "inwardly contoured" shape. In this embodiment, the
areas 42, 43 longitudinally adjacent to the contoured portions 44
are buttressed or otherwise reinforced, as illustrated in FIGS. 7
and 8. Buttressing may be accomplished, e.g., by adding material to
the buttressed portion of the catheter, thereby increasing the
stiffness and/or rigidity of the catheter at the buttressed
portions. Preferably, the inward contour is flattened out at the
buttressed portions, as best shown in FIG. 8. Distal to the valve,
buttressed portion 42 may be established by inserting a plug into
the interior of the catheter. Proximal to the valve, buttressed
portion 43 may be created by adding a suitable filler material.
Those skilled in the art will appreciate that these are only
examples of possible ways for buttressing the catheter body, and
that other methods may be substituted for those specified
herein.
[0043] As a still further alternative, catheter 50 may be
co-extruded in a manner such that the inwardly contoured segment 52
is formed from a softer, lower durometer material, while the outer,
non-contoured portion 54 is formed from a stiffer, higher durometer
material. This embodiment is illustrated in FIG. 9. Preferably, the
co-extrusion is carried out using materials having otherwise
generally similar characteristics and properties, in order to
ensure that a strong bond may be formed between the co-extruded
portions. The co-extruded materials will also preferably have
similar thermal expansion properties, so that the overall shape of
the catheter will not change appreciably with the change in
temperature. A co-extruded catheter may be formed, e.g., by
co-extruding a 50A durometer silicone with an 80A durometer
silicone. Similarly, a catheter may be formed by co-extruding two
polyurethanes of different durometers. Those skilled in the art
will appreciate that numerous other combinations of materials for
inwardly contoured segment 52 and non-contoured portion 54 may be
co-extruded in this manner to form a suitable catheter.
[0044] Another alternative embodiment of a valved catheter 70 is
illustrated in FIGS. 10-12. Catheter 70 is a dual-lumen valved
catheter, wherein lumen 72 has a one-way valve 73, and lumen 74 has
a two-way valve 75. In the embodiment shown, the catheter wall at
each longitudinal end of two-way valve 75 is buttressed or
otherwise supported against inward deflections. At one longitudinal
end, the valve is supported by the complete circle of the catheter,
which in turn, is supported by a plug 76 positioned inside catheter
70. At the other longitudinal end, the valve is supported by the
buttressed tip 77. As still further variations, the catheter can be
provided with any combination of the alternative features described
above. Thus, for example, the number and shape of lumens may be
varied as desired. Similarly, the number of valves of the catheter
may be varied, and any desired combination of one-way and two-way
valves may be provided.
[0045] It is therefore intended that the foregoing detailed
description be regarded as illustrative rather than limiting, and
that it be understood that it is the following claims, including
all equivalents, that are intended to define the spirit and scope
of this invention.
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